The Conet Project: Recordings of Shortwave Numbers Stations is a four-CD set of recordings of numbers stations, mysterious shortwave radio stations of uncertain origin believed to be operated by government agencies to communicate with spies "in the field". The collection was released by England's Irdial-Discs record label in 1997, based on the work of numbers station enthusiast Akin Fernandez.
In keeping with its 'Free Music Philosophy', the Irdial-Discs label has made the entire collection available for download in MP3 form (along with a PDF version of the included booklet) on its website completely free of charge and encourages fans to freely distribute it on file sharing networks.
More on http://en.wikipedia.org/wiki/The_Conet_Project